The present invention generally relates to the application of filter bags to tube sheets in a baghouse and, more specifically, relates to a tool for facilitating securement of the filter bags in the tube sheet openings and methods for securing the filter bags in the openings.
Baghouses are typically employed for separating particulate-laden gases into solid particles and clean air. A typical example of the environment in which a baghouse is employed is in the asphalt industry wherein hot gases of combustion are employed to dry aggregate in a rotary drying drum. The dust and other particles from the aggregate are carried by the exhaust gases into the baghouse, where the particulate matter is filtered from the gases and the clean gas is vented to atmosphere. A conventional baghouse may comprise a large hopper into which the particulate-laden gases flow. A substantial number of filter bags depend from tube sheets located adjacent the upper end of the hopper, the bags depending into a dirty air chamber. The bags filter the particulate matter from the gas and the clean gas passes through the filter material into the bags and up through the openings in the tube sheets into a clean air chamber for discharge to the atmosphere. The solids separated from the particulate laden gases drop to the bottom of the hopper for removal. Baghouses may be portable or stationary and there may be anywhere from 300 to 1,000 bags in a typical baghouse.
The bags are essentially elongated socks open at their upper ends. Typically, they are formed to a diameter of about five to six and one-half inches and may depend from the tube sheets distances, for example from nine through sixteen feet. The throughput of a baghouse is dependent upon the aggregate area of the bags and that area may range from 5,000 square feet to 20,000 square feet. The filter bag material is conventionally a woven cloth.
It will be appreciated that, in this highly abrasive environment, the bags must be periodically replaced. Also, it is vitally important that, during the initial placement of each bag in the baghouse, as well as during its replacement, the bag seats in the tube sheet opening in a manner to ensure that the bag does not leak, i.e., provide a path other than through the filter material for communicating dirty air from the dirty air chamber into the clean air chamber above the tube sheet. Typically, the bags are secured to the tube sheets to depend therefrom by snap rings. Each ring is normally formed of a stainless steel inner ring having a band of felt material secured, for example, by adhesive, about the outer annular surface thereof. The felt material is rolled along upper and lower edges to define an annular groove therebetween for receiving the margins of the tube sheet defining the tube sheet opening. The margins of the bag adjacent its open end are preferably disposed along the outside surface of the snap ring, i.e., overlying the felt material, and are reverse-folded over the top of the ring for disposition along the inside surface thereof. The end margin of the bag is stitched to the body of the bag below the snap ring to retain the ring adjacent the bag opening. When the bag is secured to the tube sheet, the bag material overlying the felt band surrounding the inner ring engages within the annular groove defined by the felt band and the margins of the tube sheet. Consequently, with this arrangement, it will be seen that if the snap ring and bag are properly seated in the opening, there will be no leakage paths between the margins of the tube sheet defining the opening and the bag.
One of the problems, however, in installing a substantial number of bags of this type is to ensure that each bag is properly seated in the tube sheet opening to avoid any leakage between the dirty air and clean air chambers on opposite sides of the tube sheet. To install the bag, a workman typically stands on the tube sheet and collapses the snap ring such that it fits within the tube sheet opening. By releasing the ring, it snaps back or is forced to engage the margins of the tube sheet opening. However, with the bag material bunched or grouped about the ring, the bag may not properly seat against the tube sheet margins, leaving one or more openings between the snap ring and the tube sheet. Frequently, the workman will run a screwdriver around the interior of the ring in an effort to ensure proper seating and sealing to the margins of the opening. This method of seating of the upper end of the filter bag in the tube sheet, however, has not been completely satisfactory and leakages have occurred.
According to the present invention, there is provided a tool for ensuring proper seating and sealing of the snap ring and bag to the margins of the openings in the tube sheet whereby leakage paths are eliminated. The present invention also provides a method of facilitating securement of the bags in the tube sheets in a manner to ensure proper seating and sealing of the filter bags to the tube sheets. Particularly, the tool of the present invention comprises a handle, preferably an elongated shaft extending along the axis of the tool, and terminating at one end in a tool head. The head includes an annular tapered portion which tapers radially inwardly in a direction away from the tool handle. The tapered portion terminates in a diameter less than the internal diameter of the snap ring to facilitate insertion of the tool head within the snap ring and terminates at its opposite end in a diameter slightly larger than the diameter of the snap ring when engaged in the margins of the tube sheet opening. Preferably, the handle is secured to a plate which extends at right angles to the handle and from which plate the tapered annular portion projects. The tool also includes a member or sleeve slidable along the handle, preferably between the opposite ends of the tool. At the end of the handle opposite the tool head, there is provided an enlargement or stop for preventing the member or sleeve from being displaced from the handle. The stop also provides an impact surface for the member or sleeve which may be weighted. The sleeve is stopped at the opposite end by the tool head.
In using the tool hereof, the workman applies the open end of the filter bag with the snap ring to the margins of the tube sheet opening by collapsing a portion of the snap ring radially inwardly to enable it to fit within the opening. By releasing the snap ring, the workman may guide it such that the margins of the tube sheet opening lie in the annular groove along the outer surface of the felt band with the filter bag material therebetween. In order to ensure that the bag is properly seated and substantially sealed to the margin of the tube sheet opening, the workman may stand on the tube sheet and insert the annular tapered portion of the tool into the open snap ring. By pressing downwardly on the tool, the snap ring is urged uniformly radially outwardly such that the snap ring and filter bag material overlying its outer surface are seated in the opening, with the margins of the opening engaging in the groove of the felt band with the filter bag material therebetween.
In the event the tool has been pushed downwardly into the ring with such force that it is difficult to remove the tool, the weighted member or sleeve may be displaced upwardly with substantial force to impact against the tool surface at the opposite end thereof from the tool head. This impact will jar or loosen the tool head from its engagement with the snap ring, permitting the tool to be withdrawn. By performing a similar operation on each of the plurality of filter bags and snap rings, the tool ensures that the bags are properly seated and that there are no leakage paths between the dirty and clean air chambers.
In a preferred embodiment according to the present invention, there is provided a tool for seating the open end of filter bags in a tube sheet having an opening for receiving the margins of the filter bag and a flexible ring for securing the bag in the opening, the ring having a diameter substantially corresponding to the diameter of the opening, comprising an elongated handle having a generally annular tool head adjacent one end, the tool head having an annular tapered portion extending generally coaxial of the handle, the tapered portion having an outer surface tapering radially inwardly in a direction away from the handle for reception generally axially of and within the ring for urging the ring radially outwardly into seated engagement with the edges of the tube sheet opening, thereby seating the filter bag and ring in the tube sheet opening.
In a further preferred embodiment according to the present invention, there is provided a method for seating the open end of a filter bag in a tube sheet having an opening for receiving the margins of the filter bag and a flexible ring for securing the bag in the opening, the ring having a diameter substantially corresponding to the diameter of the opening, comprising the steps of disposing marginal portions of the bag adjacent the open end thereof in the opening at a location between the ring and the margins of the opening and engaging a tool having a tapered head within the ring to urge the ring radially outwardly into substantial sealing engagement in the tube sheet opening with the margins of the filter bag disposed between the ring and margins of the opening.
In a further preferred embodiment according to the present invention, there is provided a method for seating the open end of a filter bag in a tube sheet having an opening for receiving the margins of the filter bag and a ring for securing the bag in the opening, the ring having a diameter substantially corresponding to the diameter of the opening, comprising the steps of securing marginal portions of the bag adjacent the open end thereof to the ring, disposing the ring in the opening of the tube sheet and engaging a tool having a tapered head within the ring to urge the ring radially outwardly into substantial seating engagement with the margins of the tube sheet opening.
Accordingly, it is a primary object of the present invention to provide a novel and improved tool for seating and substantially sealing the filter bags of a baghouse in a tube sheet and a method of application of the filters to the tube sheet wherein the tool is simple, inexpensive, easily and readily utilized and yet is effective to ensure proper seating of the bag in the tube sheet without leakage.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.